Email marketing: what happens after you press send?

Email marketing explainedWant to know more about how email actually works? It can certainly help if you are trying to track and measure your email marketing activity. Jonathan Rodger explains what happens to emails after you press send.

Many users of email marketing are unaware of the basic mechanics of how an email is sent and received, and this can lead to unrealistic expectations of how a campaign can be tracked. Because email works so well, it is sometimes a victim of its own success!

One of the attractions of email marketing is that it is highly measurable, but unfortunately the technology on which it is based has some flaws. Here I will explain what happens when you press the send button.

1982 is where it all began, when the Simple Mail Transfer Protocol (SMTP) was released and email hasn't changed much since. Considering that billions of emails are sent each day, this is a testimony to the quality of its design.

Email construction

Like a conventional letter, each email is composed of three main elements: an envelope, a header and a body.

The envelope contains the email address of the sender and the address(es) of the recipient(s). The header contains the complete “To”, “From”, “Reply” and “Subject” details amongst other information, and finally the body contains the actual content of the email, both text and HTML.

If you delve into your email program and view the detailed properties of a message, you will see that even though a mail purports to be from a certain name and email address, these are just the envelope details and the actual ISP information, and even specific mail server that sent the email, are different and can be displayed. Here's an example:

Received: from [] (

From: "Big Company" <>

This shows that the email was sent by a mail server with the IP address '' with domain '', but it will appear to be from ''. Unfortunately, this easy masking of an email's true origin is exploited by spammers and phishers to dupe recipients into believing an email originates from a different sender.

The “send” process

Your email software (or Mail User Agent) converts your message into the email format. It then attempts a connection to the SMTP server defined in your email account settings.

The SMTP server will interrogate a Domain Name System (DNS) server to look up the exact location of the server responsible for handling incoming emails for the domain that you are sending to. This is referred to as the Mail Exchange (MX) server.

Once identified, your SMTP server will connect to the recipient's MX server and attempt to deliver the message. If successful, the recipient's mail server will look at the email alias, i.e. the part before the @ sign, and store the email for the recipient to download later.

Identifying spam

Since SMTP was first conceived, a few initiatives have been put in place to allow mail servers to verify that emails received are genuinely from the actual organisation named in the headers.

As mentioned already, an email's true sender can be easily masked. However, your ISP's mail servers will use a number of techniques including Sender Policy Framework (SPF) to determine whether the originating IP address of the email is a genuine mail server or simply a hacked machine.

Oops, where did that email go?

In theory, email should either be flagged as received, or rejected by the recipient's ISP. If rejected, a bounce message should be sent. However, this notification procedure is not foolproof. It's possible for a recipient's mail server to receive an email, notify the sending mail server that all is OK, but subsequently lose the email due to internal configuration or network errors. This is the email equivalent of a black hole.

Bounce messages can also be disabled by ISPs as a deterrent to spammers, who can use them to determine whether a user exists or not. If no bounce message is received and the email is not actually opened, it is impossible for the sender to determine whether the email was actually delivered.

So, next time you ask your network guy to explain why your marketing emails are not getting through to someone, you may be able to relate to the technical jargon you'll hear. And spare a thought for the system that was designed nearly 30 years ago!

Jonathan Rodger Is an expert contributor to Start Up Donut and the founder of Message Horizon, an email marketing service for small companies.

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